U.S. patent application number 13/266516 was filed with the patent office on 2012-03-01 for mixing screw for a fuel injector in a combustion chamber of a gas turbine, and corresponding combustion device.
This patent application is currently assigned to SNECMA. Invention is credited to Sebastien Alain Christophe Bourgois, Didier Hippolyte Hernandez, Matthieu Francois Rullaud.
Application Number | 20120047899 13/266516 |
Document ID | / |
Family ID | 41445559 |
Filed Date | 2012-03-01 |
United States Patent
Application |
20120047899 |
Kind Code |
A1 |
Bourgois; Sebastien Alain
Christophe ; et al. |
March 1, 2012 |
MIXING SCREW FOR A FUEL INJECTOR IN A COMBUSTION CHAMBER OF A GAS
TURBINE, AND CORRESPONDING COMBUSTION DEVICE
Abstract
In a fuel injection device at a base of a combustion chamber, a
mixing air inlet screw is manufactured with its peripheral holes
extending only over a sector of a circle directed towards the air's
propagation cone, wherein the remainder of the periphery of the
screw is closed. It is then possible to reduce load loss of the
injection system while obtaining an improved quality of the mix
supplied to the chamber. Such a device can be used in gas turbines
fitted with centrifugal compressors and in which the air flow
towards the combustion chamber must therefore be made
convergent.
Inventors: |
Bourgois; Sebastien Alain
Christophe; (Saint Germain Les Corbeil, FR) ;
Hernandez; Didier Hippolyte; (Quiers, FR) ; Rullaud;
Matthieu Francois; (Champagne Sur Seine, FR) |
Assignee: |
SNECMA
Paris
FR
|
Family ID: |
41445559 |
Appl. No.: |
13/266516 |
Filed: |
May 18, 2010 |
PCT Filed: |
May 18, 2010 |
PCT NO: |
PCT/EP2010/056763 |
371 Date: |
October 27, 2011 |
Current U.S.
Class: |
60/737 |
Current CPC
Class: |
F23R 3/14 20130101; F23R
3/12 20130101 |
Class at
Publication: |
60/737 |
International
Class: |
F23R 3/28 20060101
F23R003/28 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2009 |
FR |
09 53335 |
Claims
1-10. (canceled)
11. A mixing screw for a fuel injector in a combustion chamber of a
gas turbine, comprising: a general shape of a hollow cylinder
fitted with at least one angular network of feed holes traversing
the cylinder as far as the hollow, wherein the network is
irregularly distributed over a circumference of the cylinder, and
extends only over a sector of a circle.
12. A fuel mixing screw according to claim 11, wherein the sector
of a circle is less than a half-circle.
13. A fuel mixing screw according to claim 11, wherein the sector
of a circle is less than a quarter-circle.
14. A fuel mixing screw according to claim 11, wherein the feed
holes are staggered in the cylinder's axial direction.
15. A fuel mixing screw according to claim 14, wherein there are
three feed holes.
16. A fuel mixing screw according to claim 11, wherein the feed
holes have different inclinations in their angular directions.
17. A fuel mixing screw according to claim 11, wherein the feed
holes are at a relief angle, with increasing widths in their
angular directions, moving in the outer radial direction.
18. A fuel mixing screw according to claim 11, further comprising
at least one other angular network of feed holes traversing the
cylinder as far as the hollow, wherein the holes of the other
network are distributed over a circle, or over only a sector of a
circle.
19. A fuel mixing screw according to claim 11, wherein the cylinder
is outlined over a second sector of a circle in addition to the
sector of a circle over which the network of feed holes
extends.
20. A gas turbine combustion device, comprising: an annular
combustion chamber; a group of fuel injectors leading to a base of
the chamber and arranged in a circle; and means of air inlet
located before the combustion chamber, and including a propagation
cone of greater radius than the chamber, and directed towards the
combustion chamber, wherein the fuel injectors include mixing
screws having a general shape of a hollow cylinder fitted with at
least one angular network of feed holes traversing the cylinder as
far as the hollow, and the network is irregularly distributed over
a circumference of the cylinder, and extends only over a sector of
a circle, and the network of feed holes extends before a radially
outer portion of the combustion chamber for each of the mixing
screws.
Description
[0001] The subject of the invention is a mixing screw for a fuel
injector in a combustion chamber of a gas turbine.
[0002] Reference should be made to FIG. 1 for a brief description
of such a combustion chamber and its surroundings. It is demarcated
by two concentric ferrules 2 and 3, the first being internal and
the second external, and by a chamber base 4, which is flat and
annular, joining the forward edges of ferrules 2 and 3. The
representation of FIG. 1 is shown as a half-section, and the
remainder of the structure can be deduced by revolution around an
axis X of the gas turbine. Other walls demarcate an air inlet
chamber 5 surrounding combustion chamber 1 and extending in front
of it, and which is supplied with air used for combustion. The fuel
enters combustion chamber 1 by pipes 6 the end of which extends in
air inlet chamber 5 before coming to an end in front of the base 4
of combustion chamber 1, to which they are attached by an injection
device 7 including a screw of essentially cylindrical shape, and
which is hollowed out either side to allow the passage of fuel
outside pipes 6 in combustion chamber 1, whilst also being pierced
with peripheral holes leading into air inlet chamber 5 to allow
combustion air to be drawn in, and a blending with the fuel by
whirling. Pipes 6 and injection devices 7 are distributed in a
circle around combustion chamber 1, in sufficient number to allow
quite regular supply of combustion chamber 1 around its
circumference. Since it is known, this distribution has not been
represented.
[0003] A satisfactory quality of the blend, notably in respect of
its uniformity, is required for the quality of the combustion. A
satisfactory blend is generally easy to obtain when the gas turbine
is fitted with a traditional compressor in front of the combustion
chamber, which submits the air to an essentially axial flow; but it
is much less easy to obtain when the compressor has a centrifugal
end 8 and submits the air to a flow the final radius of which is
greater than that of combustion chamber 1. The air then accedes to
air inlet chamber 5 through a propagation cone 9 which imposes a
centripetal component on its flow, and impairs its regularity. One
consequence of this is a lack of uniformity of the air-fuel mix.
Another consequence is a greater load loss of the air used for the
mixing.
[0004] One object of the invention is to improve the quality of the
air-fuel mix in combustion chamber 1, notably in such gas turbines
with a centrifugal compressor 8 and propagation cone 9.
[0005] The inventors have observed that the supply of the screws of
the injection devices 7 with air was heterogeneous due to the
substantial centripetal component of the flow of the air before
chamber 4, such that it exerts a greater dynamic pressure on the
radially outer face of the screws, and such that the flow rate
entering it is greater through this face.
[0006] In accordance with the invention, a mixing screw for a fuel
injector in a combustion chamber of a gas turbine is proposed,
having the general shape of a hollow cylinder fitted with at least
one angular network of feed holes traversing the cylinder as far as
the hollow, characterised in that the said network is irregularly
distributed over a circumference of the cylinder, and extends only
over a sector of a circle. This screw may be used in a combustion
device as described, including an annular combustion chamber, a
group of fuel injectors leading to a base of the chamber and
arranged in a circle, and a means of air inlet located before the
combustion chamber, and including a propagation cone of greater
radius than the chamber, and directed towards the combustion
chamber, characterised in that the fuel injectors include mixing
screws in accordance with the foregoing, and the network of feed
holes extends before a radially outer portion of the combustion
chamber for each of the said mixing screws.
[0007] By eliminating a portion of the area of drilling of the
screws, a smaller number of feed holes must be relied on to
nebulise the fuel, but an improved carburation quality was obtained
despite this simplification of the flow outline, which however
apparently increases the heterogeneousness of the operating
conditions of the mix; and the load loss of the air was reduced,
notably by eliminating the holes traversed by the least energetic
flow.
[0008] The angle covering the feed holes may be small, preferably
less than a half-circle or even a quarter-circle, and the number of
feed holes is then very small: there may advantageously be only
three such.
[0009] With a small number of feed holes it is conceivable and
often advantageous to choose them with different characteristics
and, for example, to stagger them in the axial direction of the
screw, or to incline them differently in terms of angular
direction, or to give them different drilling sections or different
relief angles in the outer radial direction.
[0010] The characteristic screw of the invention may also include
other networks of feed holes, the latter being uniformly
distributed over the circumference according to the customary
design or, on the contrary, also being in accordance with the
invention.
[0011] The invention will now be described with reference to the
figures:
[0012] FIG. 1, already described, illustrates a combustion chamber
and its surrounds,
[0013] and FIGS. 2 and 3 illustrate the invention, where FIG. 2 is
an axial section of the injection device including the screw, and
FIG. 3 is a section along line III-III of FIG. 2 through the feed
holes of the screw.
[0014] Injection system 7 is represented in detail in FIG. 2. Screw
10 is inserted between an end 11 to which pipe 6 is connected, and
a bowl 12 extending through the base of chamber 4. End 11 and bowl
12 are known models. Screw 10 includes one or more networks of air
feed holes, two in this case, one of which, which is close to end
11, is a primary screw 13, and the other, which is close to bowl
12, is a secondary screw 14.
[0015] Reference should also be made to FIG. 3, where screw 10 is
represented as a section through primary screw 13. It will be noted
that the latter consists of three feed holes 15, 16 and 17, which
extend only over a section of a circle of screw 10, since their
angular separations (angles A and B) are each 45.degree.
approximately. The additional sector 18 of primary screw 13 remains
solid, and does not therefore allow any air intake. Considering the
combustion chamber as a whole, holes 15, 16 and 17 are radially
directed towards the outside, and the additional sector is
therefore radially directed towards the inside, i.e. towards axis
X. This concerns each of the injection devices 7.
[0016] The air originating from air inlet chamber 5 therefore
enters screw 10 through feed holes 15, 16 and 17 and reaches the
central hollow 19 of screw 10, where it is whirled as it mixes with
the fuel. It was observed that the load loss of the air between
propagation cone 9 and primary screw 13 was small, and that the mix
obtained was uniform. It can be seen in FIG. 2 that feed holes 15,
16 and 17 can advantageously be staggered axially in order to
reduce the overlaps between the air vortices originating from the
different feed holes 15, 16 and 17 in central hollow 19. It is
possible to give feed holes 15, 16 and 17 different opening
sections, different phase angles (inclinations relative to the
radii of screw 10: angles C, D and E) and also different relief
angles 20, 21 and 22, i.e. widenings in the angular direction of
feed holes 15, 16 and 17 at their external portions on the side of
the inlet of the air in order to favour its intake. Relief angles
20, 21 and 22 can be extended through all or part of the depth of
holes 15, 16 and 17. Simulation tests and calculations will enable
all these settings to be adjusted; the main point is to grasp that
their adjustment is made possible by the small number of feed holes
15, 16 and 17 and by their incomplete extension over a circle which
gives great latitude to modify their shapes or their positions
without excessive complexity.
[0017] A possible disadvantage of the screw according to the
invention is its greater weight if axial staggering of the holes
requires it to be lengthened; but it is possible to attenuate this
fault by contour millings 23 outside primary screw 13, over the
additional sector 18.
[0018] Secondary screw 14 represented here is traditional, i.e. it
has feed holes 24 distributed regularly around its circumference:
for this reason it has not been represented in detail. Since there
are more feed holes 24, their section is smaller than that of feed
holes 15, 16 and 17 and primary screw 13. The number and indeed the
presence of secondary screws are not, however, critical, and they
could also be in accordance with the invention.
* * * * *